Lab report ( I do not have access to the final lab report because my groupmates have unshared it with me)
The Effectiveness of Salt vs. Sugar on the Freezing Point Depression of Water
Light Skins
The City College of New York
March 28, 2024 – April 18, 2024
Budget: $145.29
Abstract – (Alexis)
Both sodium chloride (salt) and sucrose (sugar) have common applications in cooking and food preservation. During winter, construction workers and city maintenance crews turn to these substances for de-icing roads. This is achieved through the phenomenon known as “Freezing Point Depression,” wherein the addition of a solute like salt to a solvent like water lowers the freezing point below 0°C. This study explores both sucrose and sodium chloride, considering factors such as the solution’s molality, the Van ‘t Hoff factor of the solute, and the molal freezing-point-depression constant of the solvent. The goal is to determine which substance yields a higher freezing point and thus proves more effective in de-icing roads. Using a styrofoam cup, we create an iced saltwater bath to lower the water temperature to -10°C, recording the substances containing sodium chloride and sucrose to approximate their freezing points. Preliminary findings indicate that sodium chloride, with a Van ‘t Hoff factor of two compared to sucrose’s one, demonstrates superior performance due to its higher ion concentration. Therefore, our expected result is that sucrose is more effective than sodium chloride.
Introduction – (Yuki)
The freezing point is the temperature at which a liquid becomes a solid. The melting point of a substance has the same temperature as its freezing point, however, it’s the transformation from a solid to a liquid. For example, water has a freezing point temperature of 0℃, meaning that it will start to form into ice cubes at that temperature or any lower. This implies that water has a melting point temperature of 0℃, so ice cubes will melt into water at that temperature or any higher. However, if salt is added to the water, the freezing point of the salt water decreases. In other words, the salt water has a lower freezing point than water. The difference between the freezing point of the salt water and the pure water is known as the freezing point depression. This principle refers to the phenomenon that the freezing point of the pure solvent (usually a liquid) lowers when a solute is added. A common application of this principle is seen during winter when salts are spread on slippery roads to melt the ice and snow.
Salt has become the most commonly used de-icing agent because it is cost-effective. However, there are also several drawbacks in using salt including an increase in rusting of metal surfaces on vehicles and infrastructure, deterioration of road surfaces, and environmental pollution due to salt runoff. The widespread usage of salt for winter road treatment has raised concerns on the adverse effects on the environment. A previous study has found that amphibians living in water with high salinity experience a decrease in their survivorship, weight, and activity (Sanzo and Hecnar, 251). These impacts on amphibians affect the organisms’ ability to predation and can lead to population decay or even extinction, affecting a whole ecosystem. Furthermore, salt runoff from roads results in soil contamination impacting the plant’s growth rate and health. Another study has shown that plants living in high soil salinity experience a decrease in growth rate, resulting in shorter leaves and root systems (Laffray et al. 266). Due to the high concentration of salt in soil, it is harder for plants to intake water, lowering their ability to perform photosynthesis. Ultimately, this decrease in plant growth rate can severely affect wildlife animals, decreasing in food and habitat availability. Due to these concerns, other de-icing agents emerge to reduce the damage it has on the environment. A previous study has examined how adding sugar to salt to de-ice roads reduced the effect of salt on the environment and improved the temperature effectiveness. The study has found that using sugar with salt reduced 25–40% of salt usage and dropped the melting point of water to -45℉ (David, 476). The addition of sugar to salt for de-icing roads has shown to bring many benefits.
Therefore, the purpose of this research is to determine whether sugar is more effective than salt in de-icing roads and to analyze the relationship between the freezing point depression and the amount of de-icing agents used. The significance of this study lies in the opportunity to determine more effective de-icing agents to decrease the effects it has on the environment. Furthermore, this study will help to understand whether the spread of more or fewer substances impacts the effectiveness of de-icing agents on the freezing point depression of water. The expected results are that the sugar will cause a higher freezing point depression than salt and there is a direct relationship between the amount of solute added to the freezing point depression.
Materials and Methods – (Joshua)
Materials
This experiment begins with the use of two different sized cylinders one being 250mL and another being 100mL to see if the amount of water affects the results, A gram balance to get an exact amount of the sugar and salt poured into each styrofoam cup which was then labeled using a black permanent sharpie, and a thermometer to get the temperature of each solution and than recorded these results on a notebook
Method
First, the ice bath solution was prepared with a solution that consisted of ¾ cup of ice and 1 teaspoon of salt in a styrofoam cup. Continue this by stirring the mixtures in both cups until fully dissolved. After this the temperature of the salt ice solution which ended up being negative ten degree celsius was checked. Followed by water being poured into the salt mixture to see how long it would take to freeze at this temperature. Lastly, the thermometer was rinsed and dried so that the salt water wouldn’t mix in with the testing solutions. After the ice bath was prepared, the experiment could start which is the procedure that determines the freezing point of the testing liquids. This was started by setting up the seven different testing liquids which were three salt solutions, three sugar solutions, and a regular water liquid. Continued by using a permanent marker to label one of the testing tubes and one of the 250mL beakers as our first solution to be tested. Then measured 100mL of water with the graduated cylinder and three grams of salt and this was also repeated for the sugar solution. Then mixed the salt solution in our cup labeled solution number one and placed it in a styrofoam cup with ice while making sure to keep track of the temperature with the thermometer. Then checked every five minutes to see if any ice crystals appeared for an hour long. When the first crystal appeared, check the thermometer and the temperature at which the first ice crystal appeared was the freezing point for salt solution number one. Then repeated this process with each testing liquid/solution and recorded our results in a notebook.
